This invention relates to pumping apparatus, and more particularly, to the sealing apparatus of a master cylinder or the like.
In a pumping device such as a master cylinder, it is well known to include a piston movable to in turn move a cup seal to apply pressure to brake a vehicle. It is generally true that the outer periphery of the piston and the inner periphery of the bore define a slight clearance therebetween, and with such piston acting directly on the cup seal, it is possible over a relatively long period of operation for a portion of the cup seal to be "chewed" between such outer periphery of the piston and the inner surface of the bore, resulting in damage to said cup seal. This is particularly true as the cup seal is moved by movement of the piston past a housing port communicating with the bore, as is also well known.
Of general interest in this area are U.S. Pat. No. 1,889,987 to Heidloff, U.S. Pat. No. 2,254,937 to Dick, U.S. Pat. No. 2,656,680 to Brunner, and U.S. Pat. No. 3,391,646 to Schlosser.